Role of CeO2 in promoting the spillover in CO oxidation reaction over platinum nanoparticle-supported CeO2 catalyst

•The CO oxidation activity of Pt/CeO2 was enhanced after physically mixing CeO2 particles with Pt/CeO2.•CO spillover contributes to circumventing Pt poisoning by CO at low temperatures.•The spillover of CO is supported by the formation of carbonate peaks in the physically mixed catalyst of Pt/CeO2 and CeO2.•The reductive pretreatment enables the surface O atoms of Pt-free CeO2 to contribute to the CO oxidation at the Pt NP-CeO2 interface in the physically mixed catalyst.